The present invention relates to a transistor having a base region of a first conductivity type in which a resistive region of a second conductivity type is formed, as well as an emitter region of the second conductivity type, the resistive region being connected between the base and the emitter.
It is known to connect a resistor R between the base and the emitter of a transistor, as shown in FIG. 2, to stabilize the transistor. It is also known to form the resistor R as a diffused resistor in the same semiconductor substrate as the transistor is formed. Such a transistor is shown in FIG. 3. This transistor is fabricated by forming a p-type base region 2 in an n-type silicon slab 1 by diffusion and forming an n-type emitter region 3 in the base region 2. A separate n-type belt-shaped region 4 is formed as a resistive region in the base region 2 by the same diffusion process as the process for forming the emitter region 3. The resistive region 4 is connected with the base region 2 and also with an emitter electrode 31 formed in the emitter region 3 by metal electrodes 5 and 6, respectively.
In this transistor, a resistor is inserted between the emitter and the base and, therefore, the emitter-base junction of the transistor shows voltage-current characteristics as shown in FIG. 4. The characteristics are measured between the emitter electrode and the base electrode. When a reverse bias is applied to the junction, I.sub.EB exceeds 1 mA. When the transistor substrate is fabricated, the intrinsic value of the emitter-base junction of the transistor, i.e., between of the order of nA and of the order of .mu.A, cannot be observed. For this reason, it is impossible to remove manufactured products having substrates in which substandard emitter-base junctions are formed. As a result, products having reduced breakdown voltages or products having poor reliability are marketed.
It is an object of the present invention to provide a transistor in which a resistor is connected between the emitter and the base. The transistor is characterized in that the resistor is not connected before assembly.